Gas turbine



Sept. 9, 1947.

D. F. WARNER GASEURBINE Filed March 7. 1944 Inve ntor: Donald F. Warner,

by JV H is Attorney.

Patented Sept. 9, 1947 GAS TURBINE Donald F. Warner, Swamp'scott. Mass, as slgnor to General Electric Company, a corporation of New York Application March-7, 1944, Serial No. 525,388

The present invention relates to gas turbines and especially to gas turbines operated by gases from a combustion chamber. For best efiiciencies,

such turbines are operated at high temperatures and at high speeds, temperatures and speeds so high that it is not practical to load the turbine buckets with the usual bucket cover on account of the added centrifugal stresses. Accordingly,

the gas passages between the turbine buckets have been left open at their radial outer ends and to minimize leakage the buckets have been arranged to run with close clearance with a stationary shroud bandsurrounding .the bucket wheel. In connection with such stationary shroud bands, difiiculty has been experienced in keeping them from warping and in maintaining the desired close clearance, such difliculty being occasioned by the high temperatures of adjacent parts and the unevenness of such temperatures during operation.

One object of my invention is to provide an rected to the followin specification and to the claims appended thereto.

Referring to the drawing, the figure is a sectional view of a part of a gas turbine embodying my invention.

Referring to the drawing, l indicates a turbine wheel havin a rim 2 to which is attached a ring of turbine buckets 3. The buckets are fastened to the rim at their roots in any suitable manner. Their radial outer ends are free, being provided with neither an attached bucket cover nor with a tie wire or wires. The wheel is carried by a suitable shaft supported in bearings in a bearing housing 4. Connected to and carried by the bearing housing is an annular ring 5,th ring being provided with a flange 6 at its free end. Attached to ring 5.are walls I which define a passage or passages 8 for conveying gases from a combustion chamber or combustion chambers to a nozzle ring structure, which nozzle ring structure directs the gases to the buckets 3 of the turbine wheel. Walls 7 may represent the flattened discharge ends of a number of combustion cham-' bers arranged circumfe'rentially around the bearin housin 4, the flattened ends being directly adjacent each other so as t supply gases en- 2 Claims (01. 2 5339 tirely around the periphery of the nozzle ring structure. It may be a combustion chamber arrangement, for example, such as that shown in the application of Dale D. Streid, Serial No. 525,- 391 (docket No. 74,247), filed of even date herewith and assigned to the same assignee as the present application. The radial inner walls I of the gas discharge ends are shown as being attached to the free end of ring 5 by welding as is indicated at 9. The radial outer Walls are attached to an annular ring II] by suitable weld,- ing as is indicated at H. Ring l0 surrounds the nozzlering structure. The nozzle ring structure comprises inner and outer annular rings l2 and I3 .between which are arranged the nozzle partitions 14, the nozzl partitions definin passages for directing gases to the turbine wheel as is well understood. Attached to inner nozzle ring l2 by suitable welding is an annular flange l5 which in turn is bolted to flange 6 on ring 5. The nozzle ring structure is positioned at its periphery by a number of circumrerentially spaced pins IS, the inner ends of which engage openings in bosses formed integrally with outer ring 13,

the openings being sufiiciently large to permit of radial expansion of ring l3 with respect to ring Ill. Attachedto a flange I! on ring II] is a flange I 8 carried by a ring l9 which forms a part of the turbine casing. Attached to ring 19 is an annular wall 20 which with an annular wall 2| defines an annular discharge passage 22 for the gases discharged from the turbine buckets.

Surrounding the ring of buckets is a stationary shroud ring 23 which is arranged in spaced relation to the inner surface of Wall .19 and is supported on the right hand adjacent edge of nozzle ring l3 by a rabbeted connection comprising a flange 24 which surrounds an end of ring l3 and is centered by the ring. The end of rin 23 is positioned directly against the end of nozzle ring l3 and is held against itby means of a flange 25 on ring 23 which is engaged by a face 26 on ring I9. The flange 25, so-to-speak, is pinched between the end of ring 13 and face 26. A slight annular clearance is provided in the rabbetedjoint as is indicated at 21. Thus, stationary shroud ring 23 is supported on the end of nozzle rin I3 and is free to move radially with such essary to an understanding of the present invention, but may be as disclosed in an application, Serial No. 506,930, filed October 20, 1943, in the name of Alan Howard. It i desirable that leak-v agebetween space 29 and the space between ing rings 30 have a close running clearance with the adjacent surface of rim 2.

During operation, the nozzle structure comprising rings I2. and I3 and the nozzle partitions M are at a higher temperature than the turbine buckets 3, there being a. drop in temperature of the gases as they flow through the nozzle ring structure. Axially extending ring has a certain amount of flexibility and permits of some expansion of the nozzle ring structure as a whole. The shroud ring 13 is heated from the turbine buckets and fromthe gases passing through the turbine buckets and assume a temperature about ture. The small clearance 21 is sufficient to take care of the difference in expansion between the nozzle ring structure and shroud ring 23 due to the difference in running temperature between these parts. Aside from this, they are free to operation, the parts heat up and expand so that the clearance between the left-hand edge of nozzle ring i3 and easing l0 closes up substantially or entirely,'as dmas also the radial clearance between the right-hand edge of nozzle ring I3 and the rabbet formed by flange 24. On the other hand, the clearance between the right-hand edge of shroud 23 and the casing l9 remain open both when the parts are cold and when hot during operation. Thus it will be seen that when the parts are cold there may be some looseness in the supporting means for the shroud 23, but the design of the parts with their respective clearances is such that this looseness is not sufilcient to permit the shroud to touch thetips of the buckets 3. When the parts heat up during operation, the nozzle ring l3 expands radially as described so that the shroud 23 is accurately located relative to the buckets by means of the rabbeted connection 24, 21, the inner nozzle ring l2 being fixedly secured to the relatively cool support flange 6. It should also be noted that a certain amount of hot gas will pass through the clearance space between the right-hand end of shroud 23 and the casing l9 and circulate in the annular chamber formed therebetween. Thus the shroud ring 23, which is of comparatively light cross section, has hot gas in contact with both its inner and its outer surface so that it will be maintained at a substantially uniform temperature. This temperature, however, is'appreciably lower than the temperature of the outer nozzle ring l3, as described hereinbefore. With this arrangement; no strains are put on shroud ring 23 tending to warpit or throw it out of shape. Therefore, during operation it retains its shape and maintains the desired clearance between the ends oi. the buckets 3 and the inner surface of the shroud ring. It is to be noted that the packing rings 30 are carried by the nozzle 4 ring structure which in turn is carried by the ring 5. This means that the annular fingers 30 move along with the nozzle ring structure when the parts expand. Thus, the packing rings maintain close clearance with the rim of the wheel when both the nozzle. structure and the rim of the wheel expand radially. By the improved arrangement, leakage at both the roots and peripheries of the turbine buckets is maintained at a minimum under all operating conditions.

In accordance with the provisions of the patent statutes. I have described the principle of the same as that of the buckets, this being lower than the temperature of the nozzle ring strucoperation of my invention, together with the apparatus which I now consider to represent the best embodiment thereof; but I desire to have it understood that the apparatus shown is only illustrative and that the invention may be carried out by other means.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. In a high temperature turbine, a casing, a bearing housing supported within the casing, a turbine wheel with a shaft supported in the bearing housing and a circumferential row of shroudless buckets, nozzle means supported in the casing forsuplying operating fluid to the buckets and including inner and outer rings connected by radially extending nozzle partitions, and stationary bucket shroud means comprising a ring surrounding the bucket tips with a small radial clearance therefrom, cooperating means on the shroud and casing supporting the shroud within the casing for radial movement, said shroud ring having a circumferential edge portion abutting against an adjacent edge of the outer nozzle ring and defining therewith a rabbeted joint for centering the shroud relative to the nozzle ring, said joint having a radial clearance space whereby the nozzle ring can freely expand and contract radially relative to the shroud ring.

2. In a high temperature turbine, a casing, a bearing housing supported within the casing, a turbine wheel with a shaft supported in the bearing housing, said wheel having a circumferential row of shroudless buckets, a nozzle ring structure supported in the casing. and comprising inner and outer ring members connected by substantially radially extending partitions for supplying motive fluid to .the buckets, and a shroud ring for the buckets, cooperating means on the shroud and casing supporting the shroud within the casing for radial movement, said shroud having an edge portion which abuts against an edge of the outer nozzle ring member and an axially extending flange which surrounds such edge to form a rabbeted joint to center the shroud ring on the nozzle ring, said joint having a radial clearance space whereby differential thermal expansion may take place between shroud and nozzle ring without setting up excessive stresses in the respective parts.

DONALD F. WARNER.

REFERENCES CITED The following references are of record in the 'file of this patent:

UNITED STATES PATENTS Number Name Date 2,225,769 Conrad Dec. 24, 1940 FOREIGN PATENTS Number Country 4 Date 354,888 Great Britain Apr. 2, 1931 

